Parenteral dextrose during refeeding is associated with electrolyte deficiencies in anorexia nervosa: a route-specific analysis of oral and parenteral nutrition.

Abstract

Although oral feeding is generally preferred over parenteral nutrition during refeeding in patients with anorexia nervosa, parenteral nutrition often plays a critical role in ensuring adequate nutritional support during early refeeding and preventing underfeeding syndrome. However, few studies have examined route-specific effects on refeeding-related electrolyte deficiencies while accounting for the actual caloric intake delivered via each route. We retrospectively examined 208 admissions from 98 patients with anorexia nervosa who were hospitalized in the psychiatric ward of Ashikaga Red Cross Hospital between January 2000 and June 2025. The mean age was 35.3 ± 11.1 years, and the mean body mass index (BMI) at admission was 12.2 ± 2.2 kg/m². In 139 of the 208 admissions (66.8%), nutrition was administered via both oral and parenteral routes. Outcome variables included serum electrolyte levels (phosphorus, potassium, magnesium, and calcium) at admission, at the in-hospital nadir, and the percent decrease from admission to nadir. Explanatory variables included caloric intake via the oral route (with a regular diet and enteral formulas analyzed separately) and the parenteral route (with dextrose and non-dextrose nutrients [amino acids and lipids] analyzed separately), electrolyte provision per calorie, BMI, and admission laboratory data. Multivariable mixed-effects regression analyses were performed. Caloric intake from a regular diet, enteral formulas, and parenteral non-dextrose administration was not associated with nadir electrolyte levels or with percent decreases from admission. In contrast, higher parenteral dextrose caloric intake was significantly associated with lower nadir magnesium levels (p < 0.001) and with greater percent decreases in magnesium and calcium (p < 0.001, < 0.05, respectively). Importantly, electrolyte provision per calorie via the parenteral route was not lower than that via the oral route after accounting for reported gastrointestinal absorption rates and carbohydrate proportions in each route. These findings indicate that higher parenteral dextrose administration during refeeding is associated with electrolyte decreases. This likely reflects route-specific differences in glucose handling: parenteral nutrition delivers glucose directly and rapidly into the systemic circulation, bypassing hepatic first-pass uptake that normally buffers systemic glucose and insulin exposure during oral intake. Our findings underscore the need for heightened vigilance for electrolyte deficiencies, particularly when administering parenteral dextrose. When individuals with severe anorexia nervosa begin eating again, their bodies can develop dangerous electrolyte deficiencies such as hypophosphatemia and hypomagnesemia. This is a well-known risk during recovery, and careful nutritional management is essential. In this study, we examined whether the way nutrition is given—either by mouth or through the intravenous route—affects this risk. We found that eating food or receiving nutrition through feeding formulas did not increase the likelihood of these deficiencies. However, glucose (sugar) in intravenous nutrition, given directly into a vein, was linked to greater drops in important electrolytes, particularly magnesium and calcium. This difference may be explained by how the body processes nutrients. When food is eaten, it is first handled by the digestive system and the liver, which helps regulate how sugar enters the bloodstream. In contrast, glucose given through a vein bypasses this process and enters the bloodstream rapidly, which may place more strain on the body’s balance. These findings suggest that while intravenous nutrition can be necessary in individuals with severe anorexia nervosa, special attention is needed when giving glucose in this way. Careful monitoring of electrolytes is especially important during this phase of recovery.